1. Field of the Invention
The present invention relates generally to novel coating processes for coating substrates, such as advanced composite structures, aluminum, titanium, steel, etc., to prevent or retard damage caused by oxidation, moisture, erosion, fouling, salt spray, wear, ultraviolet radiation, impact, temperature extremes and chemicals. The surfaces of such substrates, particularly on structures on ships, military and commercial aircraft experience significant damage and degradation due to these causes and therefore must be protected to avoid failure and frequent repair or replacement.
2. State of the Art
A wide variety of protective coatings are known for application to such surfaces to prevent or reduce degradation due to one or more of the aforementioned causes. Some such coatings are bondable only to metal surfaces and/or provide protection against damage caused by only certain ones of the aforementioned factors. Also, many such coatings are applied by means of volatile organic solvents or vehicles which are environmentally and physically dangerous and/or contain heavy metals such as chromium, cadmium, lead, etc., which likewise are dangerous and objectionable. Most such coatings are not repairable and/or require application temperatures which preclude use on installations such as fueled aircraft, housings for electronic equipment, etc.
Reference is made to U.S. Pat. No. 5,530,050 for its disclosure of a thermal spray powder coating composition for forming abradable coatings on turbine shrouds, compressor housings and seals. The powder compositions contain 80 to 99% by weight of zirconia and 1 to 20% by weight of ceramic-coated plastic core particles. The plastic core can comprise any one of a wide variety of different types of heat-resistant plastics, including liquid crystal polymers. The compositions are sprayed onto the target surface using one or more thermal spray guns to produce abradable coatings which are only disclosed to have superior high temperatures properties.
Reference is also made to U.S. Pat. Nos. 5,216,092 and 5,296,542 which disclose extrusion and molding resin compositions comprising blends of liquid crystal polymers comprising aromatic polyesters.
Finally reference is made to U.S. Pat. No. 5,019,686 for its disclosure of known thermal spray devices and techniques, including plasma spray processes which use a high velocity gas plasma to spray powdered or particulate coating compositions onto a substrate to form a high density coating.